Natural rubber has excellent properties such as high tensile strength and small heat buildup caused by vibration. Therefore, natural rubber has been utilized in a wide variety of applications such as a tire, a belt and a rubber glove. In addition, in view of environmental protections such, as the conservation of resources and the reduction of carbon dioxide emissions, natural rubber is attracting attention as an alternative to synthetic rubber.
However, natural rubber is also known to be inferior in heat resistance, oil resistance, ozone resistance, etc. in comparison with, synthetic rubber. Therefore, in order to superadd excellent properties to natural robber without sacrificing the outstanding properties of natural rubber, attempts to modify natural rubber through grafting, epoxidation, hydrogenation, etc. have been made thus far. For example, in Patent Citations 1 and 2, a technology for graft-copolymerizing a monomer with an unsaturated bond onto deproteinized natural rubber is introduced. In addition, in Patent Citation 3, a technology for forming crosslinking junctions between rubber molecules through a reaction, of a monomer having two or more vinyl groups to natural rubber latex is introduced.